Thanks for writing your query.
can result in pain in muscles known as myalgia
This occurs due to biochemical changes in muscles due to fever.
You can do hot fomentaton on her legs in addition to the medicines she is taking. This will help in decreasing pain in her legs.
Encourage her to take complete rest. This will help her to recover soon.
Also give her healthy diet including fresh fruits and vegetables.
I hope this is helpful to you.